Instruments for use with a bone anchor with plug member

ABSTRACT

Instruments for use with a bone anchoring assembly having plug member are disclosed that allow introduction of the plug member and bone cement or other liquid or pasty material into the bone anchor. The bone anchor includes a shaft having a first end and a second end, a channel extending from the first end to the second end, and a plug member which is insertable into the channel and guidable through the channel for closing the channel at the second end. The bone anchor is suitable for minimally invasive surgery in such a way a guide wire can be guided through the bone anchor and after the bone anchor has been anchored in the bone the plug member is inserted to close the open end of the bone anchor.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/222,280, filed Jul. 1, 2009, the contents ofwhich are hereby incorporated by reference in their entirety, and claimspriority from European Patent Application EP 09 164 329.6, filed Jul. 1,2009, the contents of which are hereby incorporated by reference intheir entirety.

BACKGROUND

The invention relates to instruments for use with a bone anchor with acannulated shaft and a plug member which is insertable into the shaftfor closing the shaft at one end. The instruments include an injectioncannula, a plug member introducing device, a metering device, a depthcontrol device, a plug member supplying device and a plug member storingdevice. The bone anchor and the instruments are particularly suited foruse in minimally invasive surgery (MIS).

WO 01/26568 A1 describes a bone anchor in the form of a bone screw witha screw head and a threaded shaft which includes an axial bore and aplurality of radial bores. The axial bore is open at the screw head sideand closed at the free end of the screw shaft. The known bone screw canbe anchored in the bone through injecting bone cement into the shaft.This leads to a permanent and safe fixation of the bone anchor.

A bone anchor in the form of a bone screw with a cannulated shaft isalso known from U.S. Pat. No. 5,047,030. The interior of the bone screwhas a continuous longitudinal canal with several radially extendingtransverse canals which contact the longitudinal canal. The longitudinalcanal is open at both ends of the screw, and it is possible to connect avacuum pump via a tube in the area around the screw head to apply avacuum to suck blood or other material.

WO 02/38054 A2, US 2004/0122431 A1 and US 2004/0147929 A1 disclose bonescrews with a tubular threaded portion and a tip portion which can beconnected to the tubular threaded portion. The tubular threaded portionhas a number of recesses in its wall. It is possible to fill the tubularthreaded portion with bone cement.

Minimally invasive surgery is applied in an increasing number of cases.With minimally invasive surgery in some cases guide wires are used toplace an implant at the implantation site. A minimally invasive accessis usually made percutaneously through the skin.

Based on the above, there is a need to provide a bone anchor which has abroad range of application, for example which is suitable for beingplaced at the implantation site with minimally invasive surgery andwhich can be filled with a bone cement or another substance.Additionally, there is a need to provide instruments for use with such abone anchor which allow convenient and safe hand-ling.

SUMMARY

The bone anchor according to the invention has the advantage that it canbe used in both, conventional surgery and minimally invasive surgery. Itis possible to provide plug members for existing cannulated bone screwsto render them suitable for minimally invasive surgery.

The bone anchor with the plug member prevents leaking of injected bonecement at the tip of the bone anchor. This reduces possible damages ofvascular structures.

With the instruments the plug member can be placed safely. Therefore, aflow of bone cement out of the distal end of the anchor is avoided.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features will become apparent from the description ofembodiments of the invention by means of the accompanying drawings. Inthe drawings:

FIG. 1 shows an exploded perspective view of the bone anchor accordingto one embodiment.

FIG. 2 shows the bone anchor of FIG. 1 in an assembled state when therod is fixed.

FIG. 3 shows a sectional view of the bone anchor of FIG. 2, the sectionbeing taken along a plane containing the rod axis.

FIG. 4 shows a top view of the plug member used in the bone anchor ofFIGS. 1 to 3.

FIG. 5 shows a perspective view of the plug member of FIG. 4.

FIG. 6 shows a side view of the plug member of FIG. 4.

FIG. 7 shows a sectional view of the plug member of FIG. 4.

FIG. 8 shows an enlarged sectional view of the plug member of FIGS. 4 to7 being inserted into the bone anchor.

FIG. 9 shows an enlarged sectional view of a second embodiment of thebone anchor with another plug member.

FIG. 10 shows an enlarged sectional view of a third embodiment of thebone anchor with a further plug member.

FIG. 11 shows an exploded view of a first embodiment of a tool forinserting the plug member into the bone anchor.

FIG. 12 shows a perspective view of the bone anchor with the tool ofFIG. 11 assembled with the plug member.

FIG. 13 shows a perspective view of the bone anchor with a secondembodiment of a tool in a position of injecting bone cement.

FIG. 14 shows the bone anchor with the second embodiment of the tool inan exploded view.

FIG. 15 shows steps 1) to 3) of using the bone anchor in minimallyinvasive surgery.

FIG. 16 a- to 16 c show step 4 of using the bone anchor in minimallyinvasive surgery.

FIG. 17 shows a perspective view of the bone anchor together withinstruments for using the bone anchor in minimally invasive surgery.

FIG. 18 shows an enlarged sectional view along the longitudinal axis ofthe bone anchor together with the tool instruments.

FIG. 19 shows a perspective view of a tray for storing plug members andan instrument for gripping and placing the plug members and an enlargedportion of the tray.

FIG. 20 shows an instrument for gripping and placing the plug members.

FIG. 21 shows a perspective view of a funnel for supplying plug membersto the bone anchor seen from the top.

FIG. 22 shows a perspective view of the funnel of FIG. 21 in aperspective view from below.

FIG. 23 shows a sectional view the section being taken along thecylinder axis of the funnel of FIG. 22.

FIG. 24 shows a perspective view of an injection cannula.

FIG. 25 shows the injection cannula of FIG. 24 together with the funnelshown in FIGS. 21 to 23.

FIG. 26 shows a perspective view of a metering stick to be used with theinjection cannula of FIGS. 24 and 25.

FIG. 27 shows a depth control stick to be used with the instruments andthe bone anchor shown in the previous figures, in particular FIGS. 17and 18.

DETAILED DESCRIPTION

FIGS. 1 to 8 show a first embodiment of a bone anchor according to theinvention. A bone anchoring device 1 includes a bone anchor 2 foranchoring in the bone, a receiving part 3 for receiving a rod 4, apressure element 5 acting onto the bone anchor 2 and a securing element6. The bone anchoring device 1 according to the embodiment described isdesigned as a so-called polyaxial bone screw which is characterized inthat the bone anchor 2 is held pivotably in the receiving part 3 whichcouples the bone anchor to the spinal rod 4. The angular position of thebone anchor relative to the rod can be fixed with the securing element6.

As shown in particular in FIG. 3, the bone anchor 2 includes a shaft 7with a head 8 at a first end and a free second end 9 which may be shapedas a tip. In the embodiment shown the head 8 has a shape of a sphericalsegment. Further, a bone thread 10 is provided on at least a portion ofthe outer surface of the shaft 7.

The bone anchor 2 is cannulated. It includes a substantially coaxialbore 11 which extends from the first end through the head 8 and theshaft 7 up to the second end 9. In a portion 12 adjacent to the secondend 9 the diameter of the bore is smaller than in the main part of theshaft 7, thereby producing a shoulder 13 inside the shaft 7. At the freeend of the head 8 an engagement structure 14 is provided for engagementwith a tool. In the wall of the shaft 7 a plurality of openings 15 areprovided which connect the bore 11 with the outside. The number, thesize and the arrangement of the openings 15 are designed according tothe overall dimension of the bone anchor 2 for the purpose of formingoutlets for bone cement or pharmaceutical substances to be introducedinto the bone anchor.

The diameter of bore 11 and in particular of the portion 12 is designedsuch that a guide wire which is commonly used for minimally invasivesurgery can be guided through the bone anchor 2.

The receiving part 3 is, as shown in particular in FIGS. 1 to 3,substantially cylindrically shaped with a first end 3 a and an oppositesecond end 3 b. The receiving part 3 includes a coaxial bore 16extending from the first end in the direction to the second end andtapering towards the second end 16 so that the head 8 of the bone anchoris pivotably held in the receiving part 3. Further, the receiving parthas a substantially U-shaped recess 17 starting from the first end 3 aand extending into the direction of the second end 3 b by means of whichtwo free legs 18, 18 b are formed. An internal thread 19 is provided ata portion of said free legs 18 a, 18 b for screwing in the securingelement 6. In the embodiment, the securing element 6 is an inner screw.

The pressure element 5 serves for exerting pressure onto the head 8 ofthe bone anchor when the inner screw 6 is tightened so that it pressesonto the rod 4. The pressure element 5 is designed such that it can beintroduced into the coaxial bore 16 and moved therein in an axialdirection. It includes on its side facing the head 8 a substantiallyspherical recess 20 in order to distribute the pressure onto head 8 andon its opposite side a substantially cylindrical recess 21 for receivingthe rod 4. It also includes a coaxial bore 22 for guiding a guide wireor a screw tool therethrough.

As shown in FIGS. 4 to 8 the bone anchor further includes a plug member30 for closing the bore 11 of the shaft 7 at the end portion 12 of thefree second end 9. The plug member 30 is a separate part which can beintroduced into the bore 11. In the embodiment shown in FIGS. 4 to 8 theplug member 30 includes a first cylindrical portion 31 the diameter ofwhich is such that it fits into the portion 12 of the shaft 7. At thefree end of the first cylindrical portion 31 a chamfered portion 32 maybe provided for facilitating introduction of the plug member. Oppositeto chamfered portion 32 the plug member includes a second cylindricalportion 33 the diameter of which is such that it fits to the innerdiameter of the bore 11. A transitional portion 34 between the firstcylindrical portion 31 and the second cylindrical portion 33 is providedwhich can be shaped so as to match the shape of the shoulder 13 betweenthe main portion of the bore 11 and the end portion 12 having thereduced diameter. Hence, the shoulder 13 forms a stop for theintroduction of the plug member.

At the free end of the second cylindrical portion 33 a plurality ofupstanding holding springs 35 are provided. The holding springs 35 arearranged in a circle with a diameter smaller than that of the secondcylindrical portion 33 and have elasticity so as to be resilientlymovable outwards and/or inwards. At their free ends, the holding springs35 include catches 36, respectively, for a detachable engagement with atool described later. The holding springs 35 are arranged in such amanner that their outer portions of the catches 36 do not projectoutside the diameter of the second cylindrical portion 33.

As shown in FIG. 8, when the plug member 30 is fully inserted into thebore 11 it closes the bore at the second portion 12 so that any bonecement or pharmaceutical substance which is introduced into bore 11cannot escape through the second end 9.

The material from which the bone anchor, the receiving part, thepressure element and the securing screw are made can be any materialwhich is usual for these kinds of devices, in particular, a bodycompatible metal, such as, for example, titanium or stainless steel or ametal alloy or any body compatible plastics, such as, for example, PEEK.The rod can be made of metal or plastics, depending on the application,i.e. whether the rod shall provide pure fixation or dynamicstabilisation. The material of the plug member can be the same as thematerial of the anchor or can be a different material. Suitablematerials for the plug member are in particular titanium and titaniumalloys, stainless steel used for implants and PEEK.

A second embodiment of the plug member is shown in FIG. 9. The plugmember 40 is ball-shaped with a diameter of the ball which is largerthan the inner diameter of the bore 11 in the second portion 12 andsmaller than the inner diameter of the bore 11 in the main portion theshaft 7. The ball-shaped plug member 40 is made advantageously of amaterial with a high specific weight, such as metal, so that the plugmember 40 can be introduced and falls down by its own weight.

FIG. 10 shows a third embodiment of the bone anchor with a plug member41 which differs from the plug member 30 only in that does not includethe holding springs 35 and that instead of the holding springs 35 arecess 42 is provided in the second cylindrical portion which serves forengagement with a tool. All other portions are identical to the plugmember 30.

Although a polyaxial bone screw has been shown as a bone anchoringdevice comprising the bone anchor any other bone anchor is encompassedby the invention. For example, a mono-axial bone screw wherein the headof the bone anchor 2 is shaped so as to receive the rod can be used. Thebone anchor further does not need to have a bone thread provided on theshaft. It can also be designed as a push and turn anchor having barbelements for retention in the bone. The bone anchor also can be designedas a bone nail with smooth outer surface.

Other modifications of the plug member are also conceivable. Forexample, the plug member can be disk-shaped, cone-shaped or can have anyother shape.

A first embodiment of a tool for inserting the plug member into the boneanchor is now described with reference to FIGS. 11 and 12. The tool 50is particularly suitable for inserting the plug member of the type shownin FIGS. 4 to 8. The tool 50 includes a handle 51 for gripping and aninsertion tube 52 extending through the handle 51. The insertion tube 52is hollow and has a length which is at least as long as the length ofthe shaft so as to be able to position the plug member 30 at the end ofthe bore 11. The inner diameter of the tube 52 is such that the tube 52can be placed onto the holdings 35 of the plug member so that theholding springs with the catches 36 are moved inwards to a certainextent. In this manner they are gripped at the end of the tube 52. Theinsertion tube 52 may have at its end a recess cooperating with thecatches 36. The outer diameter of the tube 52 is slightly smaller thanthe inner diameter of the bore 11, so that the insertion tube 52 can beintroduced into bore 11. The insertion tube 52 extends through thehandle 51 so that the open end 53 of the tube 52 is substantially flushwith the end portion of the handle 51. FIG. 11 shows the anchor 2, theplug member 30 and the tool 50 in an exploded view. In therepresentation of FIG. 12 the plug member 30 is gripped by the tool 50.Since the tube 52 extends through the handle 51 it is possible to guidea guide wire through the open end 53 into the tube portion.

FIGS. 13 and 14 show two positions of a second embodiment of the toolwith respect to the bone anchor.

The tool 60 according to this embodiment is formed by a syringe 60. Thesyringe 60 is particularly suitable for injection of bone cement orpharmaceutical substances into the bone anchor 2. It includes a barrelwith a handle 61 for gripping and a plunger 62 for pushing the bonecement or the substance into a needle or tube 63. The needle or tube 63is designed so as to be able to grip the plug member 30 or to engageinto the recess 42 of the plug member 41. The needle or tube 63 is longenough so that the plug member can be placed at the end of the bore 11.

Modifications of these tools are also conceivable. For example, theinsertion tubes 52 or 63 can be flexible so as to be adaptable tonon-straight channels in the bone anchor. Any other gripping mechanismwith, for example, release function for gripping and releasing the plugmember is possible.

Use of the bone anchor is now described with respect to FIGS. 15 and 16.FIGS. 15 and 16 show the implantation of the bone anchor with minimallyinvasive surgery. In step 1) a guide wire 100 is placed percutaneouslythrough the skin 101 to the final position of the bone anchor in avertebra 102 of the vertebral column. The plug member is not insertedinto the bone anchor as this stage of the procedure. Thereafter, thebone anchor 2 or, as shown in FIG. 15, the bone anchor preassembled withthe receiving part 3 and the pressure element 5 is provided and theguide wire 100 is guided through the bone anchor and the receiving part3 from the first end 9 of the bone anchor. Next, as shown in step 2) thebone anchoring device 1 is guided along the guide wire 100 to thevertebra 102 which is the final implantation site and is finally screwedinto the pedicle. Thereafter, as shown in step 3) the guide wire isremoved.

FIGS. 16 a) to c) show step 4) which is the introduction of the plugmember. As shown in FIG. 16 a) the tool 50 is used to introduce the plugmember 30 into the bone anchor 2. FIG. 16 b) shows a side view and FIG.16 c) a sectional view of an enlarged portion of the anchor 2 with theplug member 30 inserted by the tube 52. The plug member 30 is gripped bythe tube 52 of the tool 50 and the tube 52 is introduced into the boneanchor. The plug member 30 is then detached from the tool by insertingthe guide wire 100 (not shown) and pushing the guide wire 100 againstthe plug member so that the plug member finally rests on the shoulder 13and closes the bone anchor. Thereafter, bone cement or a pharmaceuticalsubstance is injected which exits through the openings 15 into thesurrounding bone material. It cannot exit through the free end 9 of thebone anchor since the free end 9 is closed by the plug member. Thisresults in a safe fixation, since there is no leakage of bone cement atthe free end 9 which could loosen the anchor or damage vascularstructures.

In case of the plug member 40 which is ball-shaped, the plug member 40is only introduced into the upper portion of the bore 11 so that itfalls down by its own weight and closes the free end 9.

In an alternative manner the plug member 30 or 41 is gripped by theneedle 63 of the syringe 60 containing the bone cement or thepharmaceutical substance and the plug member is injected throughinjection of the bone cement or the pharmaceutical substance into bore11 until it closes the free end.

After at least two bone anchors are anchored, the rod 4 is inserted andfixed with the securing element.

Instruments for use with the bone anchor described in the aboveembodiments are now described with reference to FIGS. 17 to 27. Theinstruments are particularly applicable for minimally invasive surgery(MIS). The instruments include an anchor extension device 200, aninjection cannula 201, a funnel 202, a depth control stick 203, ametering stick 204, a plug member supplying device 205 and a plug memberstoring device 206. The instruments are particularly useful for the boneanchor with the ball-shaped plug member 40, since they allow safe andeasy placement of the plug member.

The anchor extension device 200 includes an outer tube 210 and an innertube 211. In its portion facing away from the bone anchor 2 the outertube 210 includes an internal thread 212 which serves for cooperatingwith an external thread of the inner tube 211. In the upper portionwhich includes the internal thread 212, the anchor extension device 200has a first hole 213 which enables visual inspection of the position ofthe inner tube 211 within the outer tube 210. Further, the anchorextension device 200 includes a second hole 214 through which a pin 215which is attached to the inner tube 211 is guided. The second hole 214serves as a stop for pin 215 in an axial direction and thus limits theaxial positions of the inner tube 211 with respect to the outer tube210.

The inner tube 211 has, as shown in FIG. 18, a tube portion and tworesilient arms 211 a, 211 b providing a flexible clamping of thereceiving portion 3. The anchor extension device can be designed in manyways and is not limited to the above embodiment. The anchor extensiondevice should allow introduction of the injection cannula therein andcentering the injection cannula, for example, with centering rings.

In use, the anchor extension device is attached to the receiving part 3of the bone anchor. It serves as guidance and protection for furthermanipulations to be done at the bone anchor, in particular for using theinjection system described below. The anchor extension device 200 is notlimited to the detailed embodiment shown. Different anchor extensiondevices are already known and can be used.

The injection cannula is shown in FIGS. 18, 24 and 25 and consistsessentially of a tube 218, the inner diameter of which is dimensionedsuch that the ball-shaped plug member 40 which is described with respectto the second embodiment, can pass through the tube 218. The size of theinner diameter is large enough so as to allow the injection of bonecement. The tube 218 has a first end which faces the bone anchor and asecond end which is opposite to the first end and which includes anannular projection 219 serving as a stop for inserting the injectioncannula into the anchor extension device 200. At the free end near theannular projection 219 the injection cannula includes a connectionstructure 220 in the form of a Luer lock projection for connecting it toa syringe for injecting the bone cement. The outer diameter of tube 218is at least in a portion extending from the free end such that the tube218 can be introduced into the bone anchor 2. In the remaining portion,the injection cannula may have sections 221, 222 with different largerdiameters which are, however, small enough so as to allow theintroduction of the injection cannula into the inner tube 211 of theanchor extension device. The sections 221 are bumpers that are attachedto the injection cannula in order to provide centering of the injectioncannula inside the anchor extension device 200. The total length of theinjection cannula is such that when the injection cannula is introducedinto the anchor extension device it extends into the bore 11 of the boneanchor 2 when the annular shoulder 219 abuts the upper rim of the anchorextension device.

FIGS. 21 to 25 show a plug member supplying device funnel 202 and theinjection cannula. The funnel 202 is substantially cylindrically shapedand has coaxial bore 223 the diameter of which is larger than thediameter of the ball-shaped plug member 40 so that the ball-shaped plugmember 40 can pass through the bore 223. As shown in FIGS. 21 and 23,the funnel 202 has an upper funnel-shaped section 224 which faces awayfrom the injection. On its side opposite to the funnel-shaped portion224 the funnel includes an inner portion with a connection structure 225for connecting it to the injection cannula. The connection structure 225can have, for example, a Luer lock structure. The funnel 202 serves asan aid for introducing the ball-shaped plug member 40. Since theball-shaped plug member 40 has a minuscule size it is difficult tohandle. With the funnel the supply opening for the ball-shaped plugmember is enlarged which facilitates introduction of the plug member.

The supply of the plug member is now described with respect to FIGS. 19and 20. The device for supplying the plug members is in the embodimentshown a forceps 205 which can be designed as a non-locking forceps or asa locking forceps which has crossing arms. At the free gripping end 226of the forceps 205 a gripping structure 227 is provided. In theembodiment shown the gripping structure is formed as a hole or anindentation with a diameter which is smaller than the larger diameter ofthe ball-shaped plug member 40. The gripping structure is provided atthe portions of the arms facing each other. If the plug member hasanother shape, the gripping structure 227 can be adapted thereto. Withthe forceps, the plug member can be gripped precisely.

The forceps 205 and the plug members are stored in plug member storingdevice which is according to the embodiment shown in FIG. 19 a tray 206with a lid 228. The lid can slide in grooves to open and close the tray.In the tray a plurality of indentations or countersunk areas 229 areprovided for holding the plug members. The tray has channel-likeindentations 230 which allow the ball-shaped plug members to roll fromone storing area to the other when they escape from one storing area229. The tray has a bottom with a grid-like structure. Hence, it issuitable for vapour sterilization. The tray is also used foradministering the plug members before or during surgery. Other plugmember supplying devices are conceivable. For example, the plug membersupplying device can be designed similar to a box supplying a prescribednumber of pills.

Next, a metering stick 204 is described with reference to FIG. 26. Themetering stick 204 is formed as a cylindrical stick the outer diameterof which is smaller than the inner diameter of the bore 11 of the boneanchor 2 so that the metering stick 204 can be guided through theinjection cannula. At one end the metering stick 204 includes an annularplate 231 which serves as a handle for gripping the metering stick andas a stop to limit the introduction of the metering stick into theinjection cannula. The metering stick can be used to press bone cementwhich is located in the dead volume of the injection cannula into thebone anchor.

Finally, a depth gauge or depth control stick 203 is provided as shownin FIG. 27. The depth control stick is a cylindrical stick the length ofwhich is greater than the length of the total system from the opening 9of the bone anchor until the upper end of the injection cannula, whenthe injection cannula is connected to the bone anchor. The diameter issmaller than the diameter of the bore 11 of the bone anchor. The depthcontrol stick 203 may have markings 240 which serve for determining theposition of the plug member. The plug member should be positioned at thebottom of the bore 11 of the bone anchor to avoid a coverage of theradial bores. The depth control stick can be used to press the plugmember in its resting position at the bottom of the bore. With themarkings it can be checked whether the plug member is in its restingposition. The markings can be made for various lengths of bone anchors.

In use, after the anchor extension is fixed to the receiving part 3 ofthe bone anchor the injection cannula is inserted and the funnel 202 ismounted to the injection cannula. A suitable plug member 40 in form ofthe ball-shaped plug member is selected and picked out of the tray bymeans of the forceps. Since the ball-shaped plug member 40 is held inthe gripping structure 227 of the forceps, the ball-shaped plug member40 cannot escape during transport to the injection cannula. Then, theball-shaped plug member 40 is put into the funnel-shaped portion 224 ofthe funnel 202 where it falls through the bore 223 and enters theinjection cannula. Thereafter, the position of the plug member ischecked by using the depth control stick. If the plug member is not yetin its final position, the depth control stick is used for pressing downthe plug member to fully close the opening 9.

Then, a syringe containing bone cement is attached to the injectioncannula, for example via the Luer lock connection. The bone cement isinjected and enters the bone anchor where it escapes through the radialopenings. If the prescribed amount of bone cement has been injected, thesyringe is detached. The bone cement remaining in the injection cannulais pressed down via the metering stick 204 until the injection cannulais empty and all bone cement has reached the bone anchor

While a particular form of the disclosure has been illustrated anddescribed, it will be apparent that various modifications can be madewithout departing from the spirit and scope of the disclosure.Accordingly, it is not intended that the disclosure be limited, exceptas by the appended claims.

1. A method of attaching a bone anchoring assembly to a bone, the boneanchoring assembly comprising a shaft having a first end and a secondend, a channel extending from the first end to the second end, and aplug member configured to be insertable into the channel from the firstend and guidable through the channel to close the channel at the secondend, the method comprising: attaching the shaft to a bone; gripping theplug member with a gripping structure of a forceps adapted to a portionof the shape of the plug member; moving the forceps toward the first endof the shaft while the plug member is gripped by the gripping structure;and releasing the plug member from the gripping structure of the forcepsat the first end of the shaft to insert the plug member into the channelfrom the first end.
 2. The method of claim 1, wherein the grippingstructure is provided at least one arm of the forceps.
 3. The method ofclaim 1, wherein the gripping structure is formed by a sphericallyshaped recess adapted to grip a ball-shaped plug member.
 4. The methodof claim 1, wherein the gripping structure includes two recesses locatednear the free end of each arm of the forceps which are facing eachother.
 5. A method of attaching a bone anchoring assembly to a bone, thebone anchoring assembly comprising a shaft having a first end and asecond end, a channel extending from the first end to the second end,and a plug member configured to be insertable into the channel from thefirst end and guidable through the channel to close the channel at thesecond end, the method comprising: attaching the shaft to a bone;connecting a funnel to the first end of the shaft, the funnel having abore sized to pass the plug member therethrough; and introducing theplug member into the channel by guiding the plug member into the firstend of the shaft through the funnel.
 6. The method of claim 5, furthercomprising connecting a connection portion of the funnel to a connectorportion of an injection cannula before introducing the plug member intothe channel through the funnel, the connection portion of the funnellocated on the funnel opposite to a funnel-shaped portion of the funnel,the injection cannula comprising a tube portion adapted to be introducedat least partly into the channel and a connector portion adapted to beconnected with a syringe.
 7. The method of claim 6, further comprising:removing the funnel from the connector portion of the injection cannulaafter introducing the plug member into the channel with the funnel;connecting a syringe to the connector portion of the injection cannula;and injecting material into the bone anchor with the syringe.
 8. Themethod of claim 5, wherein the plug member is introduced into afunnel-shaped portion of the funnel, and wherein the introduction devicecomprises a tube portion connected to the funnel-shaped portion anddefining a bore sized so that the plug member can pass therethrough. 9.A method of attaching a bone anchoring assembly to a bone, the boneanchoring assembly comprising a shaft having a first end and a secondend, a channel extending from the first end to the second end, and aplug member configured to be insertable into the channel from the firstend and guidable through the channel to close the channel at the secondend, the method comprising: attaching the shaft to a bone; closing thechannel at the second end with the plug member; introducing an injectioncannula into the channel; and injecting material into the channelthrough the injection cannula.
 10. The method of claim 9, furthercomprising: connecting a syringe to a connector portion of the injectioncannula having a structure adapted to be connected to a correspondingstructure of the syringe, the injection cannula comprising a tubeportion connected to the connector portion; introducing the tube portioninto the channel; and injecting material from the syringe into thechannel.
 11. The method of claim 10, wherein the tube portion has aninner diameter which is large enough that the plug member is guidabletherethrough.
 12. The method of claim 10, wherein the connector portionis a Luer lock portion.
 13. The method of claim 9, further comprisingpressing the material through the channel with a metering device havinga stick portion sized so as to be insertable into the injection cannula.14. The method of claim 13, further comprising holding a handle at oneend of the stick portion of the metering device to press the materialthrough the channel.
 15. A method of attaching a bone anchoring assemblyto a bone, the bone anchoring assembly comprising a shaft having a firstend and a second end, a channel extending from the first end to thesecond end, and a plug member configured to be insertable into thechannel from the first end and guidable through the channel to close thechannel at the second end, the method comprising: attaching the shaft toa bone; inserting the plug member into the channel; pressing the plugmember downward to close the channel at the second end with a stickportion of a depth control device, the stick portion having a smallerdiameter than an internal diameter of the channel and having a lengthsufficient for pressing the plug member downward to close the channel atthe second end.
 16. The method of claim 15, further comprising measuringa distance or position with markings on the stick portion.
 17. A plugmember storing device and a bone anchoring assembly comprising: a boneanchor comprising: a shaft having a first end and a second end; and achannel extending from the first end to the second end; a plug memberwhich is insertable into the channel from the first end and guidablethrough the channel for closing the channel at the second end; and theplug member storing device comprising a tray and a lid, the tray havingindividual storing sections configured to store a plurality of the plugmembers.
 18. A kit of instruments for use with a bone anchor comprisinga shaft having a first end and a second end, and a channel extendingfrom the first end to the second end, and a plug member which isinsertable into the channel from the first end and guidable through thechannel for closing the channel at the second end, the kit comprising:at least one of an injection cannula, a plug member introduction device,a metering device, a depth control device, a plug member supplyingdevice, and a plug member storing device.
 19. A bone anchoring systemcomprising: a bone anchor comprising: a shaft having a first end and asecond end; and a channel extending from the first end to the secondend; a plug member which is insertable into the channel from the firstend and guidable through the channel for closing the channel at thesecond end; a plug member supplying device comprising a forceps havingtwo arms with free ends and a gripping structure for gripping the plugmember, the gripping structure being adapted to a portion of the shapeof the plug member; and wherein the gripping structure includes a recessnear the free end of each arm and wherein the recesses face each other.20. A bone anchoring system comprising: a bone anchor comprising: ashaft having a first end and a second end; and a channel extending fromthe first end to the second end; a plug member which is insertable intothe channel from the first end and guidable through the channel forclosing the channel at the second end; and a plug member introductiondevice comprising a funnel having a bore sized so that the plug membercan pass therethrough.